RESUMO
Flowering is an important agronomic trait that often depends on the integration of photoperiod, vernalization, gibberellin and/or autonomous signaling pathways by regulatory proteins such as FLOWERING LOCUS T (FT), a member of the phosphatidylethanolamine-binding protein (PEBP) family. Six PEBP family proteins control flowering in the model plant Arabidopsis thaliana, and their regulatory functions are well established, but variation in the number and structural diversity of PEBPs in different species means their precise functions must be determined on a case-by-case basis. We isolated four novel FT-like genes from Nicotiana tabacum (tobacco), and determined their expression profiles in wild-type plants and their overexpression phenotypes in transgenic plants. We found that all four genes were expressed in leaves under short-day conditions, and at least NtFT3 expression was restricted to phloem companion cells. We also found that the NtFT1, NtFT2 and NtFT3 proteins are floral inhibitors (atypical for FT-like proteins), whereas only NtFT4 is a floral inducer. We were unable to detect the expression of these genes under long-day conditions, suggesting that all four tobacco FT-like proteins may control flowering in response to short days. Phylogenetic analysis of PEBP family proteins and their functions in different solanaceous species confirmed that gene duplication and divergence within the FT-like clade has led to the evolution of antagonistic regulators that may help to fine-tune floral initiation in response to environmental cues.
Assuntos
Flores/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Nicotiana/crescimento & desenvolvimento , Proteína de Ligação a Fosfatidiletanolamina/metabolismo , Sequência de Bases , Flores/genética , Flores/fisiologia , Flores/efeitos da radiação , Regulação da Expressão Gênica de Plantas , Giberelinas/metabolismo , Luz , Dados de Sequência Molecular , Fenótipo , Floema/genética , Floema/crescimento & desenvolvimento , Floema/fisiologia , Floema/efeitos da radiação , Proteína de Ligação a Fosfatidiletanolamina/genética , Fotoperíodo , Filogenia , Reguladores de Crescimento de Plantas/metabolismo , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Análise de Sequência de DNA , Transdução de Sinais , Fatores de Tempo , Nicotiana/genética , Nicotiana/fisiologia , Nicotiana/efeitos da radiaçãoRESUMO
Hydroponically cultivated Nigella sativa L. plants treated with methyl jasmonate (MeJA) showed a twelve-fold increase in levels of the monodesmosidic triterpene saponins alpha-hederin and kalopanaxsaponin I (KsI) in the leaves. We will demonstrate that these two saponins accounted for approximately 10% of the dry plant matter, of which 93% was KsI and 7% alpha-hederin. To address the molecular basis of saponin induction by MeJA, we cloned and characterized the beta-amyrin synthase gene (NsbetaAS1) encoding one of the key enzymes in triterpene saponin biosynthesis. As expected, NsbetaAS1 transcription was induced by MeJA and led to the production of beta-amyrin when over-expressed in yeast.
